Silicon germanium (SiGe) is desirable for a p-type channel material of a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) since it has a higher hole mobility than that of silicon (Si). For instance, Non-patent Document 1 describes a p-channel MOSFET (pMOSFET) in which SiGe is used for a channel material. In the pMOSFET, in order to reduce a level density of carrier trap (hereunder referred to as “an interface trap density”) at an interface between semiconductor and an oxide layer in a MOS structure (hereunder referred to as “a MOS interface”), used is a Si passivation technique in which a surface of SiGe is covered with a Si layer and then an oxide layer is formed.
Non-patent Document 2 indicates that Si is selectively oxidized at a MOS interface in which SiGe is used as semiconductor and consequently Ge is piled up, resulting in increase in the interface trap density. Non-patent Document 3 describes results in which an oxide layer with a high dielectric-constant (a HfAlO layer) is formed on a SiGe surface on which nitridation with ammonia (NH3) has been performed, and then interface characteristics and electric properties are evaluated. Non-patent Document 4 describes that misfit dislocation in a SiGe layer that is formed on a Si wafer increases as a temperature of thermal treatment increases.
The above mentioned Non-patent Document 1 is C. Le Royer et al., “First demonstration of ultrathin body c-SiGe channel FDSOI pMOSFETs combined with SiGe(:B) RSD: Drastic improvement of electrostatics (Vth,p tuning, DIBL) and transport (μ0, Isat) properties down to 23 nm gate length”, IEDM, 16.5.1(2011), Non-patent Document 2 is S. S. Iyer et al., “A gate-quality dielectric system for SiGe metal-oxide-semiconductor devices”, EDL, 12, 246(1991), Non-patent Document 3 is J. Huang et al., “A Study of compressively strained Si0.5Ge0.5 metal-oxide-semiconductor capacitors with chemical vapor deposition HfAlO as gate dielectric”, APL, 90, 023502(2007), and Non-patent Document 4 is R. Hull et al., “In situ observations of misfit dislocation propagation in GexSi1-x/Si(100) heterostructures”, APL, 52, 1605(1988).